A. Regulations Not Retroactive. The regulations prescribed by this chapter shall not be construed to require the removal, lowering or other changes or alterations of any structure or tree not conforming to the regulations as of the effective date of the ordinance codified in this chapter, or otherwise interfere with the continuance of a nonconforming use. Nothing contained in this chapter shall require any change in the construction, alteration or intended use of any structure, the construction or alteration of which was begun prior to the effective date of the ordinance codified in this chapter, and is diligently prosecuted and completed within two years of the adoption of the ordinance codified in this chapter.

B. Permits. Before any nonconforming structure or tree may be replaced, substantially altered or repaired, rebuilt or allowed to grow higher or replanted, a permit shall be secured from the city planning commission authorizing such replacement, change or repair. No permit shall be granted that would allow the establishment or creation of an airport hazard or permit a nonconforming structure or tree or nonconforming use to be made or become higher or become a greater hazard to air navigation than it was on the effective date of the ordinance codified in this chapter, or than it was when the application for such permit is made. No such permit shall be required to make maintenance repairs or to replace parts of existing structures, or electrical distribution or telephone poles or lines, which do not enlarge or increase the height of existing structures, poles or lines. (Ord. 133 § 6, 1975)